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seccomp: Simplify handling of AUDIT_ARCH

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Currently we construct the AUDIT_ARCH variable in the Makefile, then pass
it into the C code with -D.  The only place that uses it, though is the
BPF filter generated by seccomp.sh.  seccomp.sh already needs to do things
differently depending on the arch, so it might as well just insert the
expanded AUDIT_ARCH directly into the generated code, rather than using
a #define.  Arguably this is better, even, since it ensures more locally
that the arch the BPF checks for matches the arch seccomp.sh built the
filter for.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2024-11-06 10:25:24 +11:00 committed by Stefano Brivio
parent 93bce404c1
commit 7917159005
2 changed files with 12 additions and 11 deletions
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9
Makefile
View file

@ -25,14 +25,6 @@ TARGET ?= $(shell $(CC) -dumpmachine)
TARGET_ARCH := $(shell echo $(TARGET) | cut -f1 -d- | tr [A-Z] [a-z])
TARGET_ARCH := $(shell echo $(TARGET_ARCH) | sed 's/powerpc/ppc/')
AUDIT_ARCH := $(shell echo $(TARGET_ARCH) | tr [a-z] [A-Z] | sed 's/^ARM.*/ARM/')
AUDIT_ARCH := $(shell echo $(AUDIT_ARCH) | sed 's/I[456]86/I386/')
AUDIT_ARCH := $(shell echo $(AUDIT_ARCH) | sed 's/PPC64/PPC/')
AUDIT_ARCH := $(shell echo $(AUDIT_ARCH) | sed 's/PPCLE/PPC64LE/')
AUDIT_ARCH := $(shell echo $(AUDIT_ARCH) | sed 's/MIPS64EL/MIPSEL64/')
AUDIT_ARCH := $(shell echo $(AUDIT_ARCH) | sed 's/HPPA/PARISC/')
AUDIT_ARCH := $(shell echo $(AUDIT_ARCH) | sed 's/SH4/SH/')
# On some systems enabling optimization also enables source fortification,
# automagically. Do not override it.
FORTIFY_FLAG :=
@ -44,7 +36,6 @@ FLAGS := -Wall -Wextra -Wno-format-zero-length
FLAGS += -pedantic -std=c11 -D_XOPEN_SOURCE=700 -D_GNU_SOURCE
FLAGS += $(FORTIFY_FLAG) -O2 -pie -fPIE
FLAGS += -DPAGE_SIZE=$(shell getconf PAGE_SIZE)
FLAGS += -DPASST_AUDIT_ARCH=AUDIT_ARCH_$(AUDIT_ARCH)
FLAGS += -DRLIMIT_STACK_VAL=$(RLIMIT_STACK_VAL)
FLAGS += -DARCH=\"$(TARGET_ARCH)\"
FLAGS += -DVERSION=\"$(VERSION)\"

14
seccomp.sh
View file

@ -20,6 +20,15 @@ OUT="$(mktemp)"
[ -z "${ARCH}" ] && ARCH="$(uname -m)"
[ -z "${CC}" ] && CC="cc"
AUDIT_ARCH="AUDIT_ARCH_$(echo ${ARCH} | tr [a-z] [A-Z] \
| sed 's/^ARM.*/ARM/' \
| sed 's/I[456]86/I386/' \
| sed 's/PPC64/PPC/' \
| sed 's/PPCLE/PPC64LE/' \
| sed 's/MIPS64EL/MIPSEL64/' \
| sed 's/HPPA/PARISC/' \
| sed 's/SH4/SH/')"
HEADER="/* This file was automatically generated by $(basename ${0}) */
#ifndef AUDIT_ARCH_PPC64LE
@ -32,7 +41,7 @@ struct sock_filter filter_@PROFILE@[] = {
/* cppcheck-suppress [badBitmaskCheck, unmatchedSuppression] */
BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
(offsetof(struct seccomp_data, arch))),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, PASST_AUDIT_ARCH, 0, @KILL@),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, @AUDIT_ARCH@, 0, @KILL@),
/* cppcheck-suppress [badBitmaskCheck, unmatchedSuppression] */
BPF_STMT(BPF_LD | BPF_W | BPF_ABS,
(offsetof(struct seccomp_data, nr))),
@ -233,7 +242,8 @@ gen_profile() {
sub ${__i} CALL "NR:${__nr}" "NAME:${__name}" "ALLOW:${__allow}"
done
finish PRE "PROFILE:${__profile}" "KILL:$(( __statements + 1))"
finish PRE "PROFILE:${__profile}" "KILL:$(( __statements + 1))" \
"AUDIT_ARCH:${AUDIT_ARCH}"
}
printf '%s\n' "${HEADER}" > "${OUT}"